Packaging trays are widely used at the retail level, particularly in connection with the packaging of food products. Products, such as meat, are typically packaged in trays, either pre-made or thermoformed in-line in a continuous web of thermoplastic material. Said trays are then closed by means of a flexible lid, which is sealed thereto, to guarantee the package hermeticity, and, in case of in-line thermoformed tray, the end packages are finally separated from the continuous web. In this type of packaging a continuous objective is to reduce the thickness of the plastic packaging material used for the trays, for both cost and environmental reasons. This objective however needs to be reached while still providing trays that are resistant to deformation during the industrial high speed packaging processes, as any deformation of the tray does jeopardize the hermeticity of the seal, and that do not bend when the end package is grasped and lifted, as this may prejudice safe handling at any step of the distribution chain. With the solid trays actually on the market and in particular with the in-line thermoformed trays, this is often a problem, and in particular it is a real and serious problem when the lid which is sealed to the tray is a heat-shrinkable film as the shrinkage of the lid in the packaging process will exert a certain shrink force on the tray walls and increase the risk of deformation and/or bending. A manner known to increase the rigidity of a tray without increasing its thickness is to add to the polymer material used for the manufacture of the tray an inorganic fill. This however would lead to opaque trays while the current trend is for transparent trays, as this would allow the customers to visually inspect the product they are buying from all sides and somehow guarantee their quality.
Accordingly there is still a need in the art for a thermoplastic solid tray, which may be available also as a transparent tray, endowed with an improved rigidity and improved resistance to deformation and bending, where these improvements are achieved without increasing the amount of plastic material used for its manufacture but relying on a specific geometry thereof.